1. Field of the Invention
The invention relates to devices for assisting in the positioning of cards in a card cage, specifically for the assisting in the placing of printed circuit boards into metal louver card cages.
2. Description of Prior Art
A common method for implementing electronic circuits is by use of thin, generally rectangular printed circuit boards. Such boards mechanically support various components such as integrated circuit "chips", resistors, capacitors, and transistors, as well as provide for one or more layers of electrical wiring. Such boards are easy to manufacture in quantity, and are versatile in application. Highly sophisticated electronic devices often require several boards to provide the desired functions. In order to properly support and interconnect several boards, a card cage is used.
A card cage is a box with an open side. On the side opposite the open side are usually placed electrical connectors which are cooperatively shaped and positioned to allow insertion of an edge or portion of an edge of a card, creating an electrical connection to the circuitry on each card. The connectors are themselves electrically interconnected. A popular construction technique is to use a printed circuit board, commonly called a "mother board", as the card cage side having the electrical connectors to appropriately interconnect the various cards.
In order to securely retain these various cards in the card cage, various guides are used to support the two sides of each card which are adjacent the side which has the electrical connectors. Typically, the top and bottom of the card cage will have metal louvers which form grooves or channels into which the various cards may slide. Each card portion has associated louvers on the top and bottom of the card cage, which form a pair of channels, and create a slot into which a card may slide. A printed circuit board which has been inserted into a slot is supported on three sides by the two channels at the top and bottom of the card cage, and by the mother board via the electrical connectors.
One difficulty with such card cages is that it is easy to misposition a card as it is slid into the card cage by sliding one of its edges between louvers which do not comprise part of the desired slot's channels. If a card is even slightly tilted as it is inserted into the cage, it may engage louvers which will maintain that misentry until the card is attempted to be inserted in to the electrical connectors at the rear of the slot. Since the louvers are close together to permit a tight packing of cards, it is sometimes difficult to determine which channel on the top is associated with a channel on the bottom of the card cage.
Another difficulty is that occasionally after a card cage has been designed, it is found that the louvers are insufficiently high to create a channel sufficiently deep to securely retain the cards. For instance, a production run of cards may be slightly bowed, requiring higher louvers to securely maintain the card in the channel.
Accordingly, it is an object of the invention to provide a device which assists in the proper positioning of a card in a card cage. It is an object of the invention to provide a simple method to determine which louvers on the top and bottom of a louver type card cage are associated with each other as part of a card slot. It is another object of the invention to provide a device which increases the height of the channel formed by louvers in a card cage to insure better retention of cards. Yet another object of the invention is to provide a device which enhances the guiding of a card into a card cage and which is easily added to a previously designed card cage if such is necessary.